This invention relates to a method and an apparatus for radio communication such as FDMA (frequency division multiple access) radio communication or TDMA (time division multiple access) radio communication.
In known radio communication networks between base stations and mobile stations, the base stations transmit RF signals whose carriers have respective fixed frequencies. Double-superheterodyne receivers are sometimes used in such mobile stations. In some double-superheterodyne receivers of the mobile stations, during the communcation with a base station, a frequency variation in the first local oscillator is detected by measuring both of the frequencies of the second local oscillator and the output from the second IF amplifier, and the frequency of the first local oscillator is controlled in response to the detected frequency variation so that the tuning to the RF signal from the base station can be held. These prior-art double-superheterodyne receivers have problems as follows. The frequency measurement for the detection of the frequency variation in the first local oscillator tends to make it difficult to control the frequency of the first local oscillator at a high speed. A frequency variation in the second local oscillator causes a decrease in the frequency stability of the receiver.